@mixin bg-image($url){
	background-image: url($url + "@2x.png");
  	@media (-webkit-min-device-pixel-ratio: 3),(min-device-pixel-ratio: 3){
  		background-image: url($url + "@3x.png")
  	}
  	background-repeat: no-repeat;
	background-size: 100% 100%;
}